OMF000501 GSM RN Optimization ISSUE1.4.ppt

7/30/2019 OMF000501 GSM RN Optimization ISSUE1.4.ppt

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OMF000501 GSM RN

Optimization ISSUE1.4

Wireless Training Department


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Course Contents

Concept of RN optimization

KPI of radio network

Work flow of RN optimization

Parameter adjustment principles

RN optimization tools introduction

Common problems of RN optimization


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Concept of RN Optimization

Radio network optimization means network performance

improvement utilizing existing network resources.

Steps in general

Data collection and verification

Data analysis

Parameter and hardware adjustment

Optimization result confirm and reporting

The purpose is increasing the utilization of network resourcesand solving the existing and potential problem on the network,

identifying solutions for future network planning.


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Capacity

CoverageQuality

Optimize


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Due to the mobility of subscribers and complexity of radio

wave propagation, most of network problems are caused by

increasing subscribers and the changing environments.

RN Optimization is a continuous process that is required asthe network evolves


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In the following case, the network should be optimized

New network or expansion on existing network

The network quality decreased seriously and there are many

complaints from subscribers.

An event occurs suddenly which affects the network

performance seriously.

The number of subscribers increased and affects the network

performance gradually.


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TRAFFIC

STATISTICS

DRIVE

TEST

CUSTOMER

COMPLAINTS

OPTIMIZE

Input for Optimization


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Course Contents


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KPI of Radio Network

KPI (KEY PERFORMANCE INDICATORS)

Indicates overall performance of network over a period of time

Good way to monitor network trends and anticipate future problems

Data obtained from drive test and traffic statistics


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KPI of Radio Network

Typical Radio Network KPI

BTS3

BTS4

BTS1

BTS2

KPI Parameter SourceCall Drop Rate OMC/Drive test

Congestion Rate Drive test

Handover Success Rate OMC/Drive test

Busy Hour Traffic OMC

TCH Utilization OMC

Call Setup success rate OMC/Drive test

Coverage Drive test

Quality Drive test


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Course Contents


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Flow Chart of Network Optimization


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Course Contents


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Parameter Adjustment Principles

IDENTIFY

PROBLEM

MAKE

CHANGES

MONITOR

EFFECT

MAKE

CHANGES

Parameter adjustment procedure


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Parameter Types

Radio Parameters Engineering Parameters

Handover

Parameters

Handover

Parameters

Handover

ParametersAntenna

Orientation

Antenna

D-tilt

Antenna

Height


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Adjustment of cell data parameters

Adjust the cell parameters according to the features of actual

radio channel traffic and signaling load. The parameters are for

cell select,cell reselect,call setup, handover etc, so as to

improve the overall network performance and service quality to

the end user.

Another basic principle of radio parameter adjustment is to

maximize the current network resource, traffic sharing in the the

whole network, increase the utilization of the equipment, so as

to increase the profit-investment ratio.


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According to the feature of problem to be solved, there are

two types of radio parameter adjustment.

Solve static problems: Analyze the average traffic and signaling

flows of the network and solve the network problems that

existed long time

Solve traffic overload and congestion problems during some

special period caused by special events.


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Course Contents


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Driving Test Tools

The following are the frequently used drive test tools:

TEMS and GIMS

Ant Pilot and GSM 2000

SAFCO Walkabout & SAFCO OPAS

TS9951

NEPTUNE


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Driving Test Tools

Drive test Tool application

Identify specific problems in the network

Attend to customer complaints

Perform network benchmarking with other operators

Collect periodic network data for reporting

Check coverage in new areas


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Driving Test Tools

Example: Drive test data


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Signaling Analyzer

Signaling analyzer

In real time, MA-10 signaling analyzer can trace A-bis interface

signaling message, A-G interface signaling message, SS7

signaling message of ISUP, TUP and INAP, and also bit error

rate of transmission system.

For further analysis the signaling message files can be saved

during online tracing, then they can be opened for analysis at

anytime.


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Spectrum Analyzer

Spectrum analyzer

The spectrum analyzer is mainly used to test the characteristics

of frequency, including spectrum, power of the adjacent channel,

and frequency scanning etc.


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OMC Traffic Statistics

OMC

Provides flexible means to record different information from the

network

Able to sample large amounts of data to give a better picture of

the network on a longer period of time


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OMC Traffic Statistics

Signalling test instrument

BSC performance measurement functions

TCH statistics Drop measure

Low HO suc rate

HO measurement

Incoming cell HO

Outgoing cell HO

List of alarm High block rate

Rx_q & Rx_l measure

Hardware Conk out

balance between UL & DL

List of alarmHigh drop rate

Drop call measure

Rx_q & Rx_l measure

List of alarm TCH statistics

List of alarm


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Course Contents


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Common Problems of RN Optimization

The three most important performance criterias are coverage,

capacity quality. they mainly correspond to the following

network problems:

Coverage

Congestion

Interference

Handover

TCH call drop

Dual-band network traffic distribution


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Common Problems --Coverage

Coverage

Coverage hole

Coverage hole may exist when coverage areas of two BTS

do not overlap or there are some big obstacles in the

coverage area, this lead to no signal or very poor signallevel.

Over shooting

In the actual network, the high BTS antenna can propagate

far away along a road and serve in area which its notsuppose to serve in; which result in the "isolate Island"

problem.


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Check and solve the coverage problem:

Power control measurement Function ( Statistics)

Receiving Level Measurement Function ( Statistics)

Cell Measurement Function ( Statistics)

Inter-cell Handover Measurement Function ( Statistics)


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Check the coverage problem:

Call Drop Measurement Function ( Statistics)

Defined Adjacent Measurement Function (Statistics)

Undefined Adjacent Measurement Function ( Statistics)

Outgoing Inter Cell Handover Measurement Function ( Statistics)

Rx Level data ( Drive test)


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Coverage Problem Solution:

Adjust Radio parameters

Adjust antenna parameters

Use booster, low loss combiner and tower mount amplifier

Add new site (last resort)


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Common Problems --Capacity

Capacity

TCH congestion

Check TCH congestion rate: attempted TCH seizers failure for all

(no radio resource available ) on OMC traffic statistics data, or

compare the busy hour traffic of each cell with the calculated

capacity in different GoS to judge the situation of traffic congestion .

Traffic balance

Adjust the antenna height, downtilt, and change the TX power of

BTS and MS.

Adjust parameters for cell selection, cell reselection and handover

Enable load handover and direct retry functions.


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Common Problems --Interference

How to locate the interference

Interference band in TCH Measurement Function

( Statistics)

Receiving Level Measurement Function ( Statistics)

Rx_Qual ( Drive test)


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How to locate the interference

Ratio of handovers for uplink/downlink quality ( Statistics)

Receiving Quality Measurement (Statistics)

Call drop measurement function ( Statistics)

Too many handover failure and reestablishment failures

( Statistics)


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Check and solve the interference problems

Check the place with interference and conversation quality by

drive test.

Use spectrum analyzer to find out the interference in the

frequency band.

Enable frequency hopping, DTX and power control functions.

Check and eliminate equipment problems (if any).


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Means to decrease the interference :

Increase the reuse distance between the co-frequency and

adjacent frequencies.

Decrease the transmitting power of BTS.

Adjust the antenna height, azimuth, down-tilt.

Use the anti-interference technologies, such as frequency

hopping, power control, DTX, and so on.


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Common Problems --Handover

Common handover problems:

Handover failure and handover delay lead to bad quality or

call drop.

Frequent handover decreases the conversation quality and

increases system signaling load.

Unreasonable proportion of outgoing inter-cell handover to

incoming inter-cell handover results in imbalanced traffic.


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Check and solve handover problems:

Check the handover parameters (OMC)

Inter-cell Handover Measurement Function (Statistics)

Undefined Adjacent Cell Measurement Function (Statistics)

Outgoing Inter Cell Handover Measurement Function (Statistics)

Incoming Inter Cell Handover Measurement Function (Statistics)

TCH Measurement Function (Statistics)


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Causes of abnormal handover and solutions:

The outgoing inter cell handover threshold is too low.

The adjacent cells is congested.

There are undefined adjacent cells relationship.

The handover hysteresis and handover priority are not reasonable.

The handover statistics times N and P are not set reasonable.

In HCS network coexisting with other vendors cells, the external

cellsparameters (such as LAC, CI and BCCH) must be corrected.


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Common ProblemsCall Drop

TCH call drop

During the GSM network operation, call drop is the main reason

the subscribers complain. It usually refers to the call dropped

after TCH channel seized or conversation connected, which can

be located via traffic statistics or drive test.

There are many call drop causes. Such as poor signal strength,

interference and improper parameters.

There are two important counters related call drop, radio link

timeout (RLT downlink) and SACCH multi-frame number (uplink)

sent in system information. These two counters should be set

properly according to the traffic and coverage.


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Common Problems Dual-band Network

Optimization for dual-band network

Take the following special approaches when optimize the dual-

band network, most of the approaches are same as single-band

network optimization:

When GSM 900M and GSM 1800M network belong to a same LAC

the features of two network are basically same. Parameters such as

CRO can be set flexibly according to the traffic, thus can balance

the traffic and avoid cell congestion.

When GSM 900M and GSM 1800M network has there own locationarea code, CRH and CRO should be set properly to avoid frequent

location update.

Adjust layer thresholds to balance traffic between GSM 900 and

GSM 1800


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Common Problems Dual-band Network

Dedicate mode

Idle mode Calling mode

Cell select Direct retry

Hand over

Cell reselect

Dual band network optimization elements


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Exercise

Questions

Please write down KPI for normal network

Please write down the work flow for radio network optimization

How to do for traffic balance


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Documents

OMF000501 GSM RN Optimization ISSUE1.4.ppt